Image data communication in image processing system

ABSTRACT

An image processing apparatus comprises: a reception unit adapted to receive image data transmitted from a host computer; first and second communication units adapted to communicate with a second image processing apparatus different from the image processing apparatus; a determination unit adapted to determine a type of image data; and a decision unit adapted to decide, on the basis of determination by the determination unit, whether to use the first communication unit or the second communication unit to transfer the image data.

FIELD OF THE INVENTION

The present invention relates to an image processing system such as anetwork printer and, more particularly, to a system which forms an imageon a paper medium in accordance with a PDL print job described in a pagedescription language (PDL).

BACKGROUND OF THE INVENTION

Conventionally, an image processing system has been used, in which animage forming apparatus and image reading apparatus are connected to animage processing controller connected to a PDL controller through acommand I/F and Video I/F. The PDL controller creates raster image databy rasterizing each page of a print job described in PDL into an image.The command I/F serves to exchange commands. The Video I/F serves toexchange video image data.

The PDL controller interprets a PDL job received from a host computerconnected through a network or the like to form a raster image, andsends a command sequence generated on the basis of the analysis resultto the image processing controller through the command I/F. The PDLcontroller then sends the image data to the image processing controllerthrough the Video I/F.

The image processing controller starts the image forming apparatus toform an image on a paper medium on the basis of the received commandsequence and image data, and then output the paper medium outside theapparatus (see, for example, Japanese Patent Laid-Open Nos. 8-272555,10-171617, and 11-240211).

In this conventional image processing system, image data is transferredby using the Video I/F, which is an image transfer path, regardless ofthe type of job to be processed. This Video I/F is exclusively designedfor the transfer of uncompressed raster image data. When the imageforming apparatus is a color printer, the Video I/F is designed totransfer 8-bit CMYK (four colors) signals per pixel in synchronism withan image clock. The data transfer rate of the Video I/F can besufficiently increased in accordance with the engine speed. This I/F,however, requires dedicated hardware and its control mechanism, andhence leads to an increase in cost.

In addition, the transfer of image data occupies the Video I/Fregardless of the type of image. Therefore, the next job cannot betransferred unless the transfer of the previous job is completed, evenif the job does not require high image quality or is designed to print ablack-and-white image by using an image forming apparatus capable ofcolor printing. That is, the dedicated hardware is not effectively used.

SUMMARY OF THE INVENTION

The present invention has been made in consideration of the abovesituation, and has as its object to effectively use a Video I/F which isdedicated hardware and achieve a reduction in cost.

According to the present invention, the foregoing object is attained byproviding an image processing apparatus comprising: a reception unitadapted to receive image data transmitted from a host computer; firstand second communication units adapted to communicate with a secondimage processing apparatus different from the image processingapparatus; a determination unit adapted to determine a type of imagedata; and a decision unit adapted to decide, on the basis ofdetermination by the determination unit, whether to use the firstcommunication unit or the second communication unit to transfer theimage data.

According to the present invention, the foregoing object is alsoattained by providing an image processing apparatus comprising: areception unit adapted to receive image data transmitted from a hostcomputer; a rasterization unit adapted to rasterize the image data;first and second communication units adapted to transmit the image datarasterized by the rasterization unit to a second image processingapparatus different from the image processing apparatus; a determinationunit adapted to determine a type of image data; and a decision unitadapted to decide, on the basis of determination by the determinationunit, whether to use the first communication unit or the secondcommunication unit to transfer the rasterized image data.

According to the present invention, the foregoing object is alsoattained by providing a data transfer method in an image processingapparatus having first and second communication units adapted tocommunicate with a second image processing method different from theimage processing apparatus comprising: receiving image data transmittedfrom a host computer; determining a type of image data; and deciding, onthe basis of the determined type of image data, whether to use the firstcommunication unit or the second communication unit to transfer theimage data.

According to the present invention, the foregoing object is alsoattained by providing A data transfer method in an image processingapparatus having first and second communication units adapted tocommunicate with a second image processing method different from theimage processing apparatus comprising: receiving image data transmittedfrom a host computer; rasterizing the image data; determining a type ofimage data; and deciding, on the basis of the determined type of imagedata, whether to use the first communication unit or the secondcommunication unit to transfer the rasterized image data.

Other features and advantages of the present invention will be apparentfrom the following description taken in conjunction with theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention.

FIG. 1 is a block diagram showing an arrangement of an image processingsystem according to embodiments of the present invention;

FIG. 2 is a flowchart showing a basic flow of operation at the time ofprinting in the image processing system according to the embodiments ofthe present invention;

FIG. 3 is a flowchart showing an example of the processing of switchingbetween compression and noncompression depending on image quality modesaccording to a first embodiment of the present invention;

FIG. 4 is a flowchart showing an example of the processing of switchingthe types of compression depending on color modes according to a secondembodiment of the present invention;

FIG. 5 is a flowchart showing an example of the processing of binarizinga black-and-white image according to the second embodiment of thepresent invention;

FIG. 6 is a block diagram showing another arrangement of the imageprocessing system according to the second embodiment of the presentinvention;

FIG. 7 is a flowchart showing an example of the processing to beperformed when compression/noncompression switching processing andcompression processing type switching processing are combined accordingto a third embodiment of the present invention; and

FIG. 8 is a flowchart showing an example of the processing of switchingcommunication paths depending on whether or not a security mode isdesignated according to a fourth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described indetail in accordance with the accompanying drawings.

(Arrangement of Image Processing System)

FIG. 1 is a block diagram showing the arrangement of an image formingsystem according to the embodiments of the present invention.

The image forming system according to the embodiments is comprised of animage processing controller 10, PDL controller 11, image reading unit12, and image forming unit 13.

The image processing controller 10 performs control by using a CPU 101,and includes an HDD 104, a memory (not shown), and the like. The imageprocessing controller 10 also includes a network I/F unit 102 forexchanging commands and statuses with the PDL controller 11 and a VideoI/F unit 103 for receiving raster image data from the PDL controller 11.The image processing controller 10 is connected to the PDL controller 11through these I/Fs, and is also connected to the image reading unit(e.g., a scanner) 12 and image forming unit (e.g., a printer) 13 throughI/Fs (not shown). In addition, the image processing controller 10includes a user I/F unit (not shown) having keys and a liquid crystaldisplay.

Note that, in the image processing controller 10, dedicated I/Fs areused for the image forming unit 13 and image reading unit 12 and arecomprised of control signals lines and Video data signal lines. A Videodata signal line is a signal line for transmitting or receiving imagedata. A control signal line is a signal line for transmittingtransmission/reception timing control signals for Video data and variouskinds of control instructions to the image reading unit 12 or imageforming unit 13.

The image reading unit 12 includes a CCD. The image reading unit 12 canread an image on an original set on a platen, create digital data of araster image, and send it to the image processing controller 10. Theimage reading unit 12 may include an ADF (automatic document feeder) tocontinuously read a plurality of originals.

The image forming unit 13 includes a print engine based on anelectrophotographic scheme, ink-jet scheme, or the like. The imageforming unit 13 can form an image on a paper medium on the basis of theimage data sent from the image processing controller 10, and output themedium outside the apparatus. When the image forming unit 13 includes aplurality of paper feed cassettes, a plurality of different sizes andtypes of media can be selected and fed, and images can be formed on theselected media. The image forming unit 13 may further include a specificfinishing apparatus. In such a case, a plurality of copies of documentscan be sorted and saddle-stitched in the form of a booklet.

The image processing controller 10 can compress a received image, storethe image in the HDD 104, and perform processing such as rotating it ina desired direction and enlarging or reducing it to a desired size. Theimage processing controller 10 also performs color appearance adjustmentsuch as smoothing or calibration. The image processing controller 10also includes a memory (not shown) and uses it as a work area for theseprocesses. The processes are mainly performed in a software manner bythe programs stored in a ROM (not shown) or the HDD 104 operated by theCPU 101. Obviously, however, in order to increase the processing speed,part of image processing may be implemented by hardware and performed byusing the image processing unit in the form of hardware.

The PDL controller 11 is controlled by programs operating on a CPU 111.The PDL controller 11 includes an external I/F (not shown) and receivesa print job described in a page description language (PDL) from a hostcomputer through the external I/F. The PDL controller 11 forms a printjob sequence on the basis of the received PDL job, rasterizes an image,and starts the print job. In addition, upon receiving a command from thehost computer or the like, the PDL controller 11 can execute a scan jobof sending an original read command to the image processing controller10 and sending the received image data to the host computer or the like.A network I/F unit 112 is an I/F for exchanging mainly commands andstatuses with the image processing controller 10. A Video I/F unit 113is for transmitting an image to be printed to the image processingcontroller 10. A memory 114 is used as a work area for the operation ofprograms and a frame buffer for temporarily storing the obtained rasterimage. An HDD (not shown) is also provided to store an OS, programs, jobdata, and raster images.

(Operation in Copy Mode)

The system including the image processing controller 10, image readingunit 12, and image forming unit 13 shown in FIG. 1 can perform copyoperation. When start of copy operation is instructed by the userthrough a user I/F unit (not shown), the image processing controller 10generates a copy job sequence in accordance with a copy mode such as apreset finishing or color mode.

First of all, the image processing controller 10 outputs an image readcommand to the image reading unit 12 to read image data from an originalset on the document table (not shown) of the image reading unit 12, andtemporarily stores the read image data in the HDD 104 or the framebuffer in the memory.

The image processing controller 10 then outputs a print start command tothe image forming unit 13, and sends out the image data stored in theHDD 104 or frame buffer in the order based on the copy job sequence inaccordance with the image leading end signal sent from the image formingunit 13.

If finishing operation has been designated through the user I/F (notshown), the CPU 101 designates the finishing operation mode at the timeof instructing the print start. The image forming unit 13 startsoperation in accordance with the mode designation, sequentially formssent images on paper media, and outputs them to the finishing apparatus.The finishing apparatus executes finishing operation, such as stapling,bin feeding for each specific number of media, or the like.

If the image reading unit 12 includes a DF (not shown), images can beconsecutively read from a plurality of originals set on the DF one byone. The intervals at which originals are read one by one can bedesignated by a program operating on the CPU 101 in accordance with thearrangement of the image processing controller 10. If, for example, theimage processing controller 10 has an HDD 104 or memory with asufficient capacity, all the originals may be read first, and then theimage data of the originals may be sent to the image forming unit 13 oneby one in a desired order in accordance with the form of finishing orthe like. If such a memory does not have a sufficient capacity or thetime taken for the first copy to be output (FCOT) is to be shortened,the image forming unit 13 may be started in synchronism with the startof image read operation to output an image in accordance with the imageleading timing of the image forming unit 13 every time one image isread.

In addition, in order to solve mismatches between the size and directionof a read image and those of a paper sheet on which the image is to beformed, a sequence may be generated such that each image is output tothe image forming unit 13 after processing such as enlargement/reductionand rotation is performed.

(I/F between Image Forming Unit and Image Processing Controller)

The image forming unit 13 in the embodiments can receive colormultilevel image signals and monochromatic (typically, black-and-white)binary image signals as input images. The image forming unit 13 can alsoreceive a 1- or 2-bit TAG signal for each pixel, which represents aproperty of an area in an image.

In the case of color multilevel images, the image forming unit 13receives a 32-bit signal (8 bits for each of C, M, Y and K signals) perpixel. In this case, a pixel clock is designed to form a 600-dpi imagein accordance with the image forming speed. That is, in the case ofcolor images, images are basically formed at 600 dpi. If, however, a TAGsignal is attached to a specific pixel, an image can be formed withimproved gradation characteristics by decreasing the resolution to 300dpi by pairing two adjacent pixels to one unit. That is, a TAG signal isused as a signal indicating a photographic image area to discriminate itfrom a character area, thereby allowing good image formation inaccordance with the characteristics of the respective areas. As hardwaresignal lines, four (CMYK) 8-bit signal lines and one 1-bit signal line(for TAG), i.e., a total of five signal lines, are provided. Obviously,in addition to them, control signal lines are provided. These signallines may be parallel signal lines. However, a high-speed serial linemay be used to virtually realize 5+α signal lines using drivers at thetwo ends of the line.

In contrast to this, in the case of black-and-white binary images, theimage forming unit 13 receives a 1-bit signal per pixel. In this case,an image clock is designed to form an image at 1,200 dpi. This image isa black-and-white binary image, and hence has already undergoneprocessing such as dither processing of making an image in aphotographic area have gradation characteristics in the image processingcontroller 10 or PDL controller 11. There is therefore no need to changethe processing in accordance with a TAG bit. No independent line isrequired as a hardware signal line, and the same signal line used totransfer color multilevel images can be commonly used. For example, a1-bit TAG signal line may be used as an image signal line in theblack-and-white binary mode, and may be operated in accordance with adouble-speed clock (quadruple-speed clock considering sub-scanning aswell). Alternatively, the least significant one bit for each of C, M, Yand K signals, i.e., four bits, may be used with the clock equivalent to600 dpi, and image information may be extracted as informationcorresponding to the clock equivalent to 1,200 dpi by using a driver.

Obviously, in addition to these operations, for example, 8 bits×1 colormode may be implemented for a black-and-white multilevel image. In thiscase, of the signal lines for C, M, Y and K signals, only the signalline for the K signal may be used in addition to the signal line for aTAG bit.

(I/F between PDL Controller and Image Processing Controller)

The first I/Fs between the PDL controller 11 and the image processingcontroller 10 are the network I/F units 112 and 102 using Ethernet. Thetwo controllers mainly exchange, through these I/Fs, commands such as aprint command and mode designation command and status which isinformation indicating whether or not the image forming unit 13 or imagereading unit 12 is in an operative state or whether or not an error orthe like has occurred. A general-purpose Ethernet I/F is a relativelylow-speed I/F designed to send a relatively small amount of informationat a time. However, this I/F uses a general-purpose protocol such asTCP/IP, and allows a multi-channel arrangement that exchanges aplurality of types of information at once by setting a plurality ofaddresses and ports. In the system according to the embodiments, eachnetwork I/F has purpose-specific ports such as a print port, managementport, and event port, in parallel, as independent channels. Obviously,this system may have an arrangement using serial lines such as RS232C,USB, or IEEE1394 or parallel lines such as Centronics I/Fs instead ofEthernet.

The second I/Fs are the Video I/F units 113 and 103 used fortransferring image data. These Video I/F units 113 and 103 are designedto parallelly (logically) send signals such as 8-bit C, M, Y, and Ksignals, a 1- or 2-bit TAG bit signal representing a property of animage area, a pixel clock representing a pixel unit of a signal, and aLine enable signal representing a delimiter for each line. Signal linesmay be provided by a physically necessary number. This, however, resultsin a thick cable. For this reason, several high-speed serial lines areused to virtually realize a necessary number of signal lines by usingdrivers at the two ends. Unlike the general-purpose Ethernet I/Fs usedas the network I/F units 112 and 102, the Video I/F units 113 and 103are designed exclusively in consideration of the performance of thesystem, and can transfer data at a sufficiently high rate. However, theVideo I/F units 113 and 103 are of one channel capable of sending oneimage data at a time.

(Operation in Print Mode in PDL Controller)

FIG. 2 shows a flow of operation performed in the PDL controller 11 whenprinting is carried out.

First of all, the PDL controller 11 receives a print job from a hostcomputer (not shown) through a network I/F or an external I/F (notshown) such as USB or IEEE1394 (step S101). The print job is in the PDLjob form which is described in a so-called page description language(PDL) such as PS, PCL, or LIPS, and is generated from an applicationprogram operating on the host computer or the like through a printdriver. That is, the PDL job includes information (mode designation)required to form a job sequence, for example, the size of paper sheetrequired for each page, a medium, double-sided/single-sided designation,a color mode, and finishing, and image data of each page in the PDLformat.

The PDL controller 11 extracts the mode designation from the receivedPDL job (step S102), and interprets it to form a job sequence whichindicates how many paper sheets are to be fed from which paper feedcassette, which discharge bin paper sheets are to be discharged, or anumber of paper sheets after which paper feed cassettes are to beswitched, in accordance with processing such as finishing anddouble-sided printing (step S103).

In addition, the PDL controller 11 extracts the image data portion fromthe PDL job, and converts it into raster image data which is a bitmapimage in the frame buffer area on the memory 114 (step S104). Theobtained raster image data is compressed and temporarily stored in thememory 114 or an HDD (not shown) (step S105). This operation isperformed for all the pages of the job.

The PDL controller 11 notifies the image processing controller 10 of theformed job sequence in the form of a command sequence which implementsthe job sequence through the print ports (step S106). The imageprocessing controller 10 prepares for image reception by the Video I/Funit 103 on the basis of the received job sequence. When the preparationis complete, the image processing controller 10 notifies the PDLcontroller 11 of the completion of the preparation for the reception ofimage data through the print ports.

Upon confirming the completion of the preparation of the reception ofimage data in the image processing controller 10 (YES in step S107), thePDL controller 11 transfers image data to the image processingcontroller 10 through the Video I/F unit 113 in synchronism with acontrol signal such as an image clock or Line enable signal (step S108).

Transfer processing is performed for each page, and transfer start andend commands are exchanged through the print ports on a page basis. Ifprocessing by the image processing controller 10 cannot keep up with thetransfer rate for some reason, the image processing controller 10notifies the PDL controller 11 of a reception failure, and requestsre-transmission of the image data of the same page. The processing insteps S107 and S108 is continuously repeated until the transfer of theimage data of all the pages is completed (i.e., while NO is obtained instep S109). Upon confirming the completion of the transfer of the imagedata of all the pages (YES in step S109), the print processing by thePDL controller 11 is terminated.

Note that the process shown in FIG. 2 is merely an example, and whenimage rasterization and storage processing in steps S104 and S105 forone page or more are complete, the flow may advance to step S106 toperform command sequence transmission processing so as to transmit thecommand sequence and concurrently perform image data reasterization(step S104) and image data transfer (step S108) during intervals betweencommand transmissions.

The image data sent from the PDL controller 11 to the image processingcontroller 10 is temporarily stored in the HDD 104 or the memory (notshown). At this time, the image forming unit 13 is started after thereception of all pages or one page or more depending on the settings offinishing and other various modes in the job sequence.

In starting the image forming unit 13, the image processing controller10 designates a paper feed cassette and modes such as double-sidedprinting and finishing and arranges page information associated withimage data in internal queues of the memory (not shown) in the pageorder required by the operation of the image forming unit 13 inaccordance with the job sequence transmitted from the PDL controller. Atthis time, at least image data to be transmitted first is converted inthe frame buffer in the memory, and the remaining image data stored inthe HDD 104 are sequentially transferred from the HDD 104 to the memoryas soon as the frame buffer becomes empty.

The image processing controller 10 then sends image data to the imageforming unit 13 in the order of the page information set in the queuesin synchronism with an image leading end signal from the image formingunit 13. The image forming unit 13 forms images, sent on a page basis,on media fed from the designate paper feed cassette, performs thedesignated finishing operation, and delivers the resultant media outsidethe apparatus.

(Raster Image Data Created by PDL Controller)

The PDL controller 11 in the embodiments can create two types of rasterimage data including a color multilevel image and a black-and-whitebinary image. The type of image to be created depends on a designationfrom a driver on a host computer. If no type is designated, the type ofimage to be created complies with the default designated in advance inthe PDL controller 11.

If original PDL data to be rasterized is black-and-white multilevel dataor color multilevel data which is designated to be converted intoblack-and-white data by the driver, the rasterized black-and-whitemultilevel image is converted into a black-and-white binary image. Inthis case, the multilevel image is converted into a binary image byusing the dither method or the like. In the embodiments, black-and-whitebinary data is rasterized at 1,200 dpi, and hence the resolution of acharacter and/or graphic area is changed from 600 dpi to 1,200 dpi bysmoothing processing, thereby smoothing edges and the like.

Rasterizing data on the basis of a description by the PDL language makesit possible to discriminate whether a specific area of the image is acharacter/graphic area or a bitmap image such as a photographic image.In rasterizing a given image, the image processing controller 10 alsostores such information as area information. This makes it possible touse the information for smoothing processing as in the above case ofblack-and-white binary images and the generation of TAG signals for theimage processing controller 10.

(Compression Function)

The PDL controller 11 includes compression and decompression functionsfor the obtained raster images. The PDL controller 11 compressesblack-and-white binary raster image data by a so-called JBIG scheme. TheJBIG scheme is a lossless compression scheme, and hence its compressionratio is not so high. Color multilevel raster image data can becompressed by the JPEG scheme. The JPEG scheme is a lossy compressionscheme, and hence its compression ratio is high but the image qualitydeteriorates more or less.

The PDL controller 11 temporarily compresses the raster image data andstores it in the HDD (not shown), and rasterizes the image data again onthe frame buffer in the memory 114 when transferring it via the VideoI/F unit 113. This makes it possible to perform image rasterizationwithin a processable range in advance even if transfer of the previouspage is not complete.

(Image Transfer of Black-and-White Binary Data)

When the image to be sent from the PDL controller 11 to the imageprocessing controller 10 is a color multilevel image, data correspondingto the number of pixels of (8 bits×4 colors (CMYK)+1 bit (TAG))×1 pageis an image data amount per page. If the image is a black-and-whitebinary image, the image data corresponds to the number of pixelscorresponding to 1 bit×1 page. In addition, in the embodiments, theresolution of a color image is 600 dpi, and the resolution of ablack-and-white image is 1,200 dpi. Therefore, the data amount isreduced to about ⅛.

Obviously, this data may be transmitted to the image processingcontroller 10 through the Video I/F unit 113. When, however, the dataamount is reduced to such an extent, the data can be compressed andincorporated in a command sequence to the print port upon compression.That is, the image data can be transmitted during the transmission ofthe job sequence through the network I/F unit 112. The image processingcontroller 10 receives the image data concurrently with the jobsequence, and hence need not establish synchronization with the VideoI/F unit 113. This reduces the processing load on the CPU 101.

(Other Features)

The PDL controller 11 in the embodiments can process PostScript (PS) asa PDL language. Obviously, the PDL controller 11 can be designed toprocess a plurality of PDL data such as PCL, PDF, and LIPS data.

The user can designate the quality of a desired image by the driver(PPD). In accordance with this designation, the PDL controller 11 canadjust the degree of image quality deterioration by adjusting thecompression ratio of the image to be temporarily stored in the HDD.

In addition, the user can designate color printing or black-and-whiteprinting through the driver.

First Embodiment

FIG. 3 is a flowchart showing processing in a PDL controller 11according to the first embodiment of the present invention. Thisprocessing exemplifies a case wherein a high image quality mode and lowimage quality mode are switched in accordance with the image qualitydesignation in a PDL job which is designated through a user I/F such asa print driver. The processing in the flowchart of FIG. 3 will bedescribed in detail below.

Upon reception of a PDL job from a host computer (not shown), the PDLcontroller 11 interprets the received PDL job in step S201. The PDLcontroller 11 then generates a command sequence for this PDL job byextracting a mode designation for the job, e.g., the size of each pageand medium designation. This PDL job includes the image quality modedesignation designated by the print driver.

In step S202, an image quality mode is determined. If this PDL jobcorresponds to the high image quality mode designation, the flowadvances to step S203. If the PDL job corresponds to the low imagequality mode, the flow advances to step S207.

In the high image quality mode, the page description of the PDL job isinterpreted in step S203 to rasterize the data of each page into rasterimage data (bitmap image data) on the frame buffer of a memory 114.

The raster image data created in step S204 is then queued in the imagebuffer memory (not shown) for transmission in the memory 114. At thistime, if the buffer memory has a sufficient free space, the image datathemselves may be queued in the order of pages to be transmitted. Ingeneral, however, it is difficult in terms of cost to mount a memoryhaving such a large capacity. Therefore, labels corresponding to theraster image data of the respective pages are queued, and the rasterimage data themselves are compressed and stored in the HDD (not shown)in the PDL controller 11 in association with the labels. Note that eachpage number is uniquely defined in a job, and hence assigning a uniquejob ID to a generated print job can set “job ID+page ID” as a label forraster image data. In this case, a lossless compression algorithm isused, if possible. If only a lossy compression algorithm such as JPEG isallowed to be used in consideration of the HDD capacity, circuitarrangement, and the like, compression is performed by using a highimage quality designation parameter with a compression ratio low enoughto correspond to the high image quality mode. If this image is to betransferred through a Video I/F unit 113, since the image must berasterized, it is important to use a compression scheme that allowshigh-speed rasterization.

When the rasterization of the image is complete, a command sequence istransmitted in step S205. Upon reception of the command sequence, animage processing controller 10 starts preparing for the reception of theimage. When the preparation for reception is complete, the imageprocessing controller 10 notifies the PDL controller 11 of thecorresponding information.

When the notification of the completion of the preparation for receptionis received from the image processing controller 10, the flow advancesto step S206 to transfer raster image data as Video data page by pagethrough the Video I/F unit 113. As described above with reference to theprocessing in step S204, since the image data queued in the HDD iscompressed, the data must be decompressed before Video transfer. Thisdecompression processing may be implemented by software as long as theprocessing can be done at a sufficiently high speed in accordance withthe Video transfer rate. In general, hardware dedicated to decoding ismounted to perform the processing in real time using the hardware. Inaddition, in this Video transfer, timing commands indicating a start andend for each page are independently sent through the print port.

Note that since a job is often comprised of a plurality of pages, therasterization processing and queuing processing in steps S203 and S204are repeated page by page throughout all the pages, and a commandsequence is then transmitted in step S205. Obviously, another port fortransmitting commands indicating the start and end of image transfer maybe prepared. In this case, after a command sequence is generated in stepS201, the command sequence is quickly transmitted to the imageprocessing controller 10. After the transmission, Video data may be sentto the image processing controller 10 on a page basis while raster imageis created. This allows the image processing controller 10 to know inadvance which type of image is to be sent, and hence can quickly preparefor the reception of the Video data.

If it is determined in image quality mode determination in step S202that the low image quality mode is designated, raster image data iscreated in step S207. In this case, rasterizing image data is the sameprocessing as that performed in step S203.

The created raster image data is then JPEG-compressed in step S208. Inthe first embodiment, in the low image quality mode, since image data istransferred by using a relatively low-speed command communication path,the data is JPEG-compressed in accordance with a lossy high compressionratio designation with a higher importance being placed on the amount ofdata than image quality. Using a general compression method like JPEGcompression allows the image processing controller 10 formed as adifferent hardware to use a general decompression method.

In step S209, the image data of the respective pages which areJPEG-compressed as page data are merged in the command sequencegenerated in step S201. Since a command sequence must be generated on ajob basis instead of a page basis, the processing from the creation ofraster image data in step S207 to merging of compressed image data instep S209 needs to be performed throughout all the pages of the job.

When a command sequence is generated by merging the image data of allthe pages, the command sequence is transmitted to the image processingcontroller 10 in step S210. The image processing controller 10 cansequentially rasterize images oh a page basis while receiving thecommand sequence without waiting for data from the Video I/F unit 113.

With the above processing, the data of a multilevel image for which highimage quality is designated is transmitted through the Video I/F,whereas a multilevel image for which low image quality is designated isJPEG-compressed and transmitted as data attached to a command throughthe network I/F. In this manner, compression/noncompression of imagedata and data transfer paths can be selectively used.

In general office use or the like in which very high image qualityprinting is not required, an image is transferred through a commandcommunication path unless high image quality is designated. Therefore,the Video I/F, which is low in frequency of use, need not be very fast,and hence can take a cost-saving arrangement.

In addition, assume that a port different from a port for thetransmission of a print sequence is provided on a command communicationpath to transmit commands indicating VideoStart/End. In this case, asdescribed above, in the case of a job for which the high image qualitymode is designated, since Video Data transfer is started after a commandsequence is sent, even if the Video I/F is occupied during the Videodata transfer, the next job can be concurrently sent, together withimage data, as long as a low image quality mode sufficient for generaluse is designated for the job.

The order in which image data are printed by the image processingcontroller 10 can be freely scheduled. If, therefore, an image formingunit 13 is activated in the order in which transfer of image data iscompleted, instead of the order in which command sequences are sent,regardless of the high image quality mode and low image quality mode,the image forming unit 13 can be effectively operated withoutunnecessary pauses.

As described above, in the case of a job for which high image quality isnot required, image transfer of the job can be done through a commandcommunication path in a compressed state, and hence can be sent withoutoccupying the Video I/F. This makes it possible to effectively use theVideo I/F which is dedicated hardware. In addition, decreasing theoperating ratio of the Video I/F allows the use of low-speed hardware,and hence can achieve a reduction in cost.

Second Embodiment

The second embodiment of the present invention will be described next.In the second embodiment, compression methods are switched for color andblack-and-white jobs. This processing will be described with referenceto the flowchart of FIG. 4.

In step S302, a PDL controller 11 interprets the PDL job received from ahost computer (not shown), and generates a command sequence. This PDLjob includes a color job in which all pages are formed from colorobjects, and a black-and-white job in which all pages are formed fromblack-and-white object data. The PDL job may also include ablack-and-white job designation for printing all pages comprised ofcolor objects in black-and-white.

In step S303, it is checked whether the received PDL job is a color orblack-and-white job. If the job is a color job, the flow advances tostep S304. If the job is a black-and-white job, the flow advances tostep S306.

In the case of a color job, the data of each page is rasterized in stepS304. In step S305, the data are JPEG-compressed. This processing is thesame as that described with reference to step S208.

In the case of a black-and-white job, raster image data is created instep S306. This raster image data may be binary data with each pixelconsisting of one bit or multilevel data with each pixel consisting ofeight bits, based on the original description in PDL. In the case of ablack-and-white job which is based on a color multilevel image as theoriginal PDL image and in which black-and-white job designation is made,the data is rasterized as multilevel black-and-white image data witheach pixel consisting of eight bits.

In step S307, binarization processing is performed for the obtainedraster image data. The steps in the binarization processing in step S307will be described in detail with reference to FIG. 5.

First of all, in step S402, the raster image data obtained in step S306is interpreted. In step S403, it is checked whether the data ismultilevel image data or binary image data.

In the case of multilevel image data, image area segmentation processingis performed in step S404. In the image area segmentation processingperformed in step S404, TAG bit information indicating each areainformation which has been stored upon PDL data rasterization is used,and a bitmap area is segmented into character areas and photographicareas in accordance with gradation change patterns.

In step S405, smoothing processing is performed for a character area. Inthis processing, for example, an 8×8 pixel area is enlarged into a 16×16pixel area by pattern matching to smooth edge portions. That is, a600-dpi raster image is enlarged into a 1,200-dpi image. Obviously, ahalftone character which is not in black but is in gray is smoothedwithout any change in gray level.

In step S406, an area determined as a photographic area is increased inthe number of pixels. In this processing, one pixel is simply enlargedinto four pixels without any change in gray level. With the aboveprocessing, multilevel data are converted into 1,200-dpi data throughoutthe entire image area.

Thereafter, in step S407, the multilevel image is converted into abinary image by the dither method or the like. At this time, when aphotographic area is binarized, high-frequency components are removed,and the gradation characteristics slightly deteriorate. Therefore,jaggies caused by conversion from one pixel into four pixels areabsorbed and become less noticeable. That is, better gradationcharacteristics can be obtained by expressing gradation with 1,200-dpibinary data than by 600-dpi binary data.

If it is determined in step S403 that the obtained image is originally a600-dpi binary image, the flow advances to step S408. Image areasegmentation processing in step S408 can be done by using only the TAGbit information described above.

In step S409, smoothing processing is performed for a character area asin step S405.

In step S410, the graininess of a photographic area is reduced byenlarging a 600-dpi binary dither image into 1,200 dpi image. In thisprocessing, the average density of a relatively narrow range of theoriginal image (e.g., a 5×5 pixel area) is calculated, and the density(multilevel value) of the central pixel is set to the average density.The resultant image is slightly blurred. Therefore, filtering may beperformed for edge enhancement, and the number of pixels is thenincreased as in step S406 or S407 to obtain a 1,200-dpi binary image bythe dither method or the like.

As described above, when the rasterized data is originally binary datawith each pixel consisting of one bit, only smoothing processing isperformed.

With the above processing, a good 1,200-dpi binary black-and-whiteraster image can be obtained from either black-and-white 600-dpimultilevel or binary data.

When the above binarization processing in step S307 is complete, thebinarized image is JBIG-compressed in step S308. The JBIG compressionalgorithm is a lossless compression algorithm, and allows the originalimage to be completely reconstructed by decompression. Therefore, nodeterioration in image quality is caused by this algorithm.

In step S309, the image data compressed in step S305 or S308 is mergedin a command. In this operation, image data is incorporated in thecommand sequence generated in step S302 in addition to a portion whereinformation such as a medium and size of each page is described. Thecommand sequence finally generated in this manner internally holds JPEG-or JBIG-compressed image of each page.

In step S310, the generated command sequence is transmitted. The imageprocessing controller 10 extracts image data from the received commandsequence, JPEG- or JBIG-decompresses the data, and can immediatelyperform print processing or storing in the HDD of the data.

According to the flowchart of FIG. 4, after it is discriminated whethera received PDL job is a color or black-and-white job, the data israsterized. However, color job/black-and-white job determination may bedone after rasterization depending on the structure of a PDL language.

The second embodiment has exemplified the job in which all the pages areblack-and-white or color. However, by performing the processing shown inFIG. 4 on a page basis, the present invention can be applied to a job inwhich color pages and black-and-white pages are included on a pagebasis.

In addition, processing for a black-and-white job can be applied to amonochrome job comprised of monochrome objects as well as ablack-and-white job.

According to the second embodiment, switching compression methods for acolor job and black-and-white job enables to transfer image data byusing a command communication path in each case. In this case, as shownin FIG. 6, a system can be constructed with an arrangement equivalent tothe arrangement shown in FIG. 1 from which the Video I/F units 103 and113 are omitted, thereby expecting a great reduction in cost.

In addition, in printing a black-and-white job which is high infrequency of use in offices, in particular, 1,200-dpi binary losslesslycompressed image data is used, and hence a system which can obtain agood print result with respect to a drawing constituted by characters,line drawings, and the like which is especially required in offices, andcan properly cope with color printing which is low in frequency of usecan be built at a low cost.

As described above, according to the second embodiment, performing imagetransfer of a black-and-white job by using a command communication pathin a compressed state makes it possible to send the job withoutoccupying the Video I/F. Therefore, the Video I/F which is dedicatedhardware can be effectively used. In addition, decreasing the operationratio of the Video I/F allows the use of low-speed hardware, and hencecan achieve a reduction in cost.

By performing image transfer of even a color job by using a commandcommunication path in a compressed state upon increasing the compressionratio using a lossy compression scheme, the Video I/F can be omittedfrom the system, thus achieving a reduction in cost.

Third Embodiment

The third embodiment of the present invention will be described next.

In the third embodiment, an example of a combination of the first andsecond embodiments will be described with reference to FIG. 7.

Upon reception of a PDL job from a host computer (not shown), a PDLcontroller 11 interprets the received PDL job in step S702. Note thatthe received PDL job includes a designation indicating a color job orblack-and-white job in addition to an image quality mode.

In step S703, it is discriminated whether the received PDL job is acolor job or black-and-white job. If the job is a color job, the flowadvances to step S704. If the job is a black-and-white job, the flowadvances to step S306.

In the case of a color job, an image quality mode is determined in stepS704. If a high image quality mode is designated for the PDL job (i.e.,a job determined as a color/high image quality mode job), the flowadvances to step S203. If the job is a low image quality mode job (i.e.,a job determined as a color/low image quality mode job), the flowadvances to step S304.

In steps S203 to S206, the same processing as that performed in stepsS203 to S206 in FIG. 3 is performed. A redundant description of thisprocessing is omitted.

In steps S304 and S305, the same processing as that performed in stepsS304 and S305 in FIG. 4 is performed. A redundant description of thisprocessing is omitted.

If it is determined in step S703 that the job is a black-and-white job,the processing in steps S306 to S308 is performed. The processing insteps S306 to S308 is the same as that shown in FIG. 4. In addition, thebinarization processing in step S307 is the same processing as thatdescribed with reference to FIG. 5 in the second embodiment, and hence aredundant description thereof is omitted.

In step S309, the image data compressed in step S305 or S308 is mergedin a command. In step S310, the generated command sequence istransmitted. These processes are also the same as those described in thesecond embodiment.

In the third embodiment, a black-and-white job uses an engine foroutputting 1,200-dpi binary image data. For this reason, only color jobsare selectively processed in the high image quality and low imagequality mode. However, black-and-white jobs may also be selectivelyprocessed in the high image quality mode and low image quality modedepending on the embodiment of an engine.

According to the third embodiment, since the Video I/F is not used evenfor a color job as long as it is in the low image quality mode, thefrequency of use of the Video I/F further decreases. This makes itpossible to use a more inexpensive low-speed arrangement and to outputimages with a high image quality of 1,200 dpi in the case ofblack-and-white jobs.

As described above, according to the third embodiment, in the case of ajob for which high image quality is not required or a black-and-whitejob, image transfer of the job can be done through a commandcommunication path in a compressed state, and hence can be sent withoutoccupying the Video I/F. This makes it possible to effectively use theVideo I/F which is dedicated hardware. In addition, decreasing theoperating ratio of the Video I/F allows the use of low-speed hardware,and hence can achieve a reduction in cost.

Obviously, this system can be designed to allow the user to designate animage quality mode or color mode through the print driver at the time ofprinting. Alternatively, the user may be allowed to set in advanceusable modes through the PDL controller.

It is needless to say that monochrome data can be used in place ofblack-and-white data.

In addition, it is obvious that the image forming unit can be designedto process jobs without discriminating color jobs from black-and-whitejobs. In such case, when an original mainly containing a photograph isto be processed, the high image quality mode using the Video I/F may beset. When an original mainly containing texts is to be processed, evenif it is a color original, the original data may be binarized andlosslessly compressed. Image transfer of the resultant data may beperformed through a command communication path to print the data at1,200 dpi.

Fourth Embodiment

The fourth embodiment of the present invention will be described next.

In the fourth embodiment, the PDL job transmitted from a host computeris processed by switching between data transfer through a Video I/F anddata transfer through a network I/F depending on whether or not asecurity mode is designated.

FIG. 8 is a flowchart showing the flow of processing in the fourthembodiment.

The basic flow is the same as the flowchart of FIG. 3 in the firstembodiment. Referring to FIG. 3, in step S202, an image quality mode isdetermined to determine the high image quality mode or low image qualitymode. In contrast to this, in the fourth embodiment, it is checked instep S802 whether or not the security mode is designated.

In step S801, the PDL job received from the host computer isinterpreted. If it is determined in step S802 that the security mode isdesignated, the flow advances to step S203 to transfer data through theVideo I/F. If it is determined in step S802 that the security mode isnot designated, the flow advances to step S207 to transfer data throughthe network I/F.

In steps S203 to S210, the same processing as that performed in S203 toS210 in FIG. 3 is performed. Therefore, a redundant description of thisprocessing is omitted.

The fourth embodiment has been described above. This embodiment allowsselective use of communication paths depending on whether or not the PDLjob transmitted from the host computer designates the security mode.

The flowchart of FIG. 8, with reference to which the fourth embodimentis described, has exemplified the case wherein the Video I/F is usedwhen the security mode is designated. However, when the security mode isdesignated, data may be transferred through the network I/F, whereaswhen the security mode is not designated, data may be transferredthrough the Video I/F.

In either case, if the security of a communication path used to transfera job for which the security mode is designated is improved, the job forwhich the security mode is designated can be selectively transferred insafety.

Other Embodiments

Note that the present invention can be applied to an apparatuscomprising a single device or to system constituted by a plurality ofdevices.

Furthermore, the invention can be implemented by supplying a softwareprogram, which implements the functions of the foregoing embodiments,directly or indirectly to a system or apparatus, reading the suppliedprogram code with a computer of the system or apparatus, and thenexecuting the program code. In this case, so long as the system orapparatus has the functions of the program, the mode of implementationneed not rely upon a program.

Accordingly, since the functions of the present invention areimplemented by computer, the program code installed in the computer alsoimplements the present invention. In other words, the claims of thepresent invention also cover a computer program for the purpose ofimplementing the functions of the present invention.

In this case, so long as the system or apparatus has the functions ofthe program, the program may be executed in any form, such as an objectcode, a program executed by an interpreter, or scrip data supplied to anoperating system.

Example of storage media that can be used for supplying the program area floppy disk, a hard disk, an optical disk, a magneto-optical disk, aCD-ROM, a CD-R, a CD-RW, a magnetic tape, a non-volatile type memorycard, a ROM, and a DVD (DVD-ROM and a DVD-R).

As for the method of supplying the program, a client computer can beconnected to a website on the Internet using a browser of the clientcomputer, and the computer program of the present invention or anautomatically-installable compressed file of the program can bedownloaded to a recording medium such as a hard disk. Further, theprogram of the present invention can be supplied by dividing the programcode constituting the program into a plurality of files and downloadingthe files from different websites. In other words, a WWW (World WideWeb) server that downloads, to multiple users, the program files thatimplement the functions of the present invention by computer is alsocovered by the claims of the present invention.

It is also possible to encrypt and store the program of the presentinvention on a storage medium such as a CD-ROM, distribute the storagemedium to users, allow users who meet certain requirements to downloaddecryption key information from a website via the Internet, and allowthese users to decrypt the encrypted program by using the keyinformation, whereby the program is installed in the user computer.

Besides the cases where the aforementioned functions according to theembodiments are implemented by executing the read program by computer,an operating system or the like running on the computer may perform allor a part of the actual processing so that the functions of theforegoing embodiments can be implemented by this processing.

Furthermore, after the program read from the storage medium is writtento a function expansion board inserted into the computer or to a memoryprovided in a function expansion unit connected to the computer, a CPUor the like mounted on the function expansion board or functionexpansion unit performs all or a part of the actual processing so thatthe functions of the foregoing embodiments can be implemented by thisprocessing.

As many apparently widely different embodiments of the present inventioncan be made without departing from the spirit and scope thereof, it isto be understood that the invention is not limited to the specificembodiments thereof except as defined in the appended claims.

1. A data processing apparatus comprising: a reception unit thatreceives print data transmitted from a host computer; first and secondcommunication units that communicate with an image processing apparatusdifferent from the data processing apparatus; an analyzing unit thatanalyzes the print data received by the reception unit; a determinationunit that determines whether raster image data to be generated byrasterizing the print data is of a first type or of a second type, basedon an analysis result by the analyzing unit, an amount of raster imagedata of the second type being smaller than an amount of raster imagedata of the first type; and a decision unit that decides, if thedetermination unit determines that the raster image data is of the firsttype, to use the first communication unit to transfer the raster imagedata and to use the second communication unit to transfer a printcommand for the raster image data, and, if the determination unitdetermines that the raster image data is of the second type, not to usethe first communication unit and to use the second communication unit totransfer both the raster image data and the print command for the rasterimage data, wherein the determination unit determines a designated typeof an image quality mode of the raster image data to be transferred fromthe data processing apparatus to the image processing apparatus,wherein, if the designated type of the image quality mode is determinedto be a first type, the determination unit causes the data processingapparatus to generate the raster image data with the image quality ofthe first type, and wherein, if the designated type of the image qualitymode is determined to be a second type, the determination unit causesthe data processing apparatus to generate the raster image data with theimage quality mode of the second type.
 2. The apparatus according toclaim 1, wherein, when the determination unit determines that thedesignated type of the image quality mode is a low image quality mode,the raster image data is compressed and transferred using the secondcommunication unit.
 3. The apparatus according to claim 1, wherein thefirst communication unit includes an interface for image data transfer,and the second communication unit includes a general purpose networkinterface.
 4. The apparatus according to claim 1, further comprising arasterization unit that rasterizes the received print data to generatethe raster image data, wherein the first and second communication unitstransmit the raster image data rasterized by the rasterization unit. 5.The apparatus according to claim 4, wherein the first communication unitincludes a communication unit for communicating the raster image datarasterized by the rasterization unit, and the second communication unitincludes a communication unit for communicating a command based on theprint data.
 6. A data transfer method performed by a data processingapparatus having first and second communication units that communicatewith an image processing apparatus different from the data processingapparatus, the method comprising: receiving print data transmitted froma host computer; analyzing the received print data; determining whetherraster image data to be generated by rasterization the received printdata is of a first type or of a second type, based on an analysis resultof the analyzing, an amount of raster image data of the second typebeing smaller than an amount of raster image data of the first type;deciding, if the raster image data is determined to be of the firsttype, to use the first communication unit to transfer the raster imagedata and to use the second communication unit to transfer a printcommand for the raster image data, and, if the raster image data isdetermined to be of the second type, not to use the first communicationunit and to use the second communication unit to transfer both theraster image data and the print command for the raster image; anddetermining a designated type of an image quality mode of the rasterimage data, wherein, if the designated type of the image quality mode isdetermined to be a high image quality type of mode, the raster imagedata of the first type is generated, and wherein, if the designated typeof the image quality mode is determined to be a low image quality typeof mode, the raster image data of the second type is generated.
 7. Themethod according to claim 6, wherein, when the designated type of imagequality mode is determined to be the low image quality mode, the rasterimage data is compressed and transferred using the second communicationunit.
 8. The method according to claim 6, wherein the firstcommunication unit includes an interface for image data transfer, andthe second communication unit includes a general purpose networkinterface.
 9. The method according to claim 6, further comprising:rasterizing the received print data to generate the raster image data,wherein the first communication unit and the second communication unittransfer the raster image data.
 10. The method according to claim 9,wherein the first communication unit includes a communication unit forcommunicating the raster image data, and the second communication unitincludes a communication unit for communicating a command based on theprint data.
 11. A non-transitory storage medium readable by a dataprocessing apparatus having first and second communication units thatcommunicate with an image processing apparatus different from the dataprocessing apparatus, the storage medium storing a program that isexecutable by the data processing apparatus, wherein the programincludes program code for causing the data processing apparatus toperform a method comprising: receiving print data transmitted from ahost computer; analyzing the received print data; determining whetherraster image data to be generated by rasterizing the received print datais of a first type or of a second type, based on an analysis result ofthe analyzing, an amount of raster image data of the second type beingsmaller than an amount of raster image data of the first type; deciding,if the raster image data is determined to be of the first type, to usethe first communication unit to transfer the raster image data and touse the second communication unit to transfer a print command for theraster image data, and, if the raster image data is determined to be ofthe second type, not to use the first communication unit and to use thesecond communication unit to transfer both the raster image data and theprint command for the image data; and determining a designated type ofan image quality mode of the raster image data, and wherein, if thedesignated type of the image quality mode is determined to be a highimage quality type of mode, the raster image data of the first type isgenerated, and wherein, if the designated type of the image quality modeis determined to be a low image quality type of mode, the raster imagedata of the second type is generated.
 12. The non-transitory storagemedium according to claim 11, wherein the method performed by the dataprocessing apparatus us further comprises: rasterizing the receivedprint data to generate the raster image data.